The present invention relates generally to screw top containers and specifically to such devices which reveal a prior opening by requring an alteration in their appearance when they are opened.
It is relatively easy to open and reseal a screw-cap container. This presents a potential hazard to purchasers because such containers can be opened and resealed by someone other than the purchaser. Thus, container contents may be exposed and contaminated without the purchaser being aware of it. To eliminate the danger of such unapparent prior contamination of container contents, various devices have been implemented which permit a consumer to verify that a container has not been opened before the consumer purchases the product.
One example is a screw cap that has a band with inward projections at the opening of the cap. When the cap is screwed onto a container, the projections on the band engage a protrusion on the container. The band breaks away from the cap at a perforated line when the cap is screwed off. Once opened, the cap and band cannot be restored to their original condition. However, the broken band only indicates a removal of the cap. Since it is necessary for the cap to lifted away from the bottle to break the cap from the band at the perforated line, any vacuum inside the container may be broken before the band breaks away. Therefore, it is virtually impossible to determine, upon quick inspection, if the vacuum has been broken without removing the cap. Since contaminants can enter once the vacuum breaks, this type of container sealing mechanism can provide no assurance that container contents are free of exposure to contaminants.
Another problem with the above device is that it may be unsuitable for a large-mouth container. If the above device were applied to large-mouth container, the band portion would need to be unduly large and sturdy. The band must be sturdy to transmit torque applied to the cap via the projection on the band to the protrusion on the cap. Therefore, an excessive force would then be required to break the connection between the band and the cap and thereby open the container. Thus, this type of cap is unsuitable for a large-mouth container.
Another type of tamper-revealing cap has an extended band portion which is heat-shrank to cover the container tightly. The tight fit prevents the band from rotating when the cap is rotated. The band has a perforated line which is torn when the cap is unscrewed. A large amount of torque must be generated to remove such a cap, however. This limits its utility, especially as applied to large-mouth containers.
Still another type of seal includes a ratchet mechanism on the lower end of a cap which is separated from the cap by a perforated line. The same problem of very high torque arises with this design as well.
In still another design, a label is affixed over a cap and a container body. However, since the label is easy to remove, there is a great danger that the label would be intentionally removed and reaffixed after the container is opened.